I’ve read a lot of explanations about blockchains and Bitcoin but What Satoshi Did is among the best of them.
This invention works in two parts. Constructing a shared ledger amongst all participants was the first step. By sharing the entire ledger of transactions, all participants could convince themselves that their own transactions were validly entered, that all value derived from an authentic source, and that the entire ledger balanced.
The second part was to agree on the ledger. Using induction, and agreeing on all prior ledger states, Satoshi reduced the problem to agreeing what each new appending block is. The first batch, or genesis block, was created by Satoshi. The next block, and each successive block, included a consensus signature over this block and the previous block, creating a chain of blocks, or the blockchain.